1. Field of the Invention
This invention relates to an improvement in the manufacture of hydrogen peroxide from hydrogen and oxygen.
2. Prior Art
It has been proposed by Hooper, in U.S. Pat. No. 3,361,533, that the synthesis of hydrogen peroxide from its elements, hydrogen and oxygen, can be carried out in an aqueous liquid medium capable of inhibiting the decomposition of hydrogen peroxide in the presence of a solid catalyst. The liquid medium contemplated contains water, an acid and a non-acidic oxygen-containing organic compound. The solid catalyst can be an element of Group I or Group VIII of the Periodic Table, supported on a carrier such as alumina, silica, titanium dioxide, graphite or silicon carbide. A palladium catalyst is made by deposition of palladium (II) chloride or another palladium compound on a support and reduction by hydrogen at 50.degree.-400.degree. C. However, the teaching of Hooper is that alumina, silica or alumina-silica supports are preferred for catalysts giving high yields of hydrogen peroxide.
It has further been proposed by Hooper, in U.S. Pat. No. 3,336,112, that preparation of hydrogen peroxide from its elements with a solid catalyst in the liquid phase in the presence of water can be done in the presence of a sequestrative stabilizer for hydrogen peroxide, more particularly, a condensed phosphoric acid having a degree of polymerization up to about 14. Preferably, the catalyst is supported on Al.sub.2 O.sub.3 or SiO.sub.2 or a combination.
A variety of procedures have been proposed for the preparation of palladium catalysts on activated carbon supports.
Henke et al, in U.S. Pat. No. 2,285,277, disclose preparing a hydrogenation catalyst of a noble metal, e.g., palladium, by impregnation with a noble metal compound and reduction of the resulting slurry with alkaline formaldehyde, hydrazine or hydrogen, apparently at about or above 50.degree. C.
U.S. Pat. No. 2,520,038, by Hultquist, discloses preparation of palladium on charcoal hydrogenation catalyst at a temperature substantially below that of the freezing point of water. Hydrogen is used as a reducing agent.
In U.S. Pat. No. 2,749,359, by Calkins et al, is disclosed preparation of palladium on charcoal catalysts suitable for hydrogenation. The catalyst is prepared by depositing the palladium on the charcoal, washing the coated catalyst with formic acid, washing with water, drying and reducing with hydrogen.
Hamilton et al, in U.S. Pat. No. 2,857,337, obtain palladium on charcoal or activated carbon catalysts for hydrogenation by reduction of a palladium salt with hydrogen and activation with various named metals. Formaldehyde is indicated as being an alternative for hydrogen in reducing the palladium salt.
U.S. Pat. No. 3,138,560, by Keith et al, discloses the production of palladium on carbon catalysts. Reduction is achieved either by organic chemical means, e.g., the use of aldehydes or formic acid, or by hydrogen. The use of hydrogen peroxide and hydrochloric acid in the preparation of selected catalysts is disclosed, but the reference does not contemplate treating a previously-prepared catalyst with HCl prior to use.
U.S. Pat. No. 3,736,265 by Suggitt, discloses catalysts of Group VIII metals on carbon. These are heated to from 700.degree. F. to 1100.degree. F. (371.degree. C. to 593.degree. C.) for two to eight hours in the presence of hydrogen. In the case of palladium catalysts, loss of activity is said to be prevented by heat treating for 1-24 hours at temperatures from 500.degree. to 1200.degree. F. The catalysts can be regenerated using a stream of hydrogen under the same conditions of time and temperature utilized for initial stabilization.
Schrage, in U.S. Pat. No. 3,736,266, also discloses a palladium on carbon hydrogenation catalyst. Hydrogen and formaldehyde are cited as conventional reducing agents.
U.S. Pat. No. 3,864,281, by Ohorodnik et al, discloses a palladium catalyst utilized for dehalogenation, in which the carrier can be activated carbon or silicic acid. Reduction with hydrogen or with an alkaline hydrazine solution is indicated.
Schmitt, Jr., et al, in U.S. Pat. No. 4,035,260, disclose hydrogenation catalysts which comprise platinum metal on a preformed porous carbon support. Reduction of the metal is achieved with hydrogen.
U.S. Pat. No. 4,093,559 by Fernholz et al, discloses palladium catalysts used for the oxacylation of olefins. Among suitable carriers is active charcoal. Among cosolvents for the palladium compound being impregnated are ketones. The use of a ketone to treat a previously prepared catalyst is not suggested.
Although a variety of techniques have been disclosed for preparing palladium on carbon catalysts for hydrogenation and other chemical reactions, the present state of the art does not provide any palladium on carbon oxidation catalysts which effectively catalyze the production of hydrogen peroxide from its elements and also do not catalyze decomposition of thus-produced hydrogen peroxide to a commercially unacceptable extent.